Visual electron flow indicator



1953 s. MALOOF 2,648,795

VISUAL ELECTRON FLOW INDICATOR I Filed Aug. 9, 1951 2 Sheetis-Sheet 1 frzaeiziar 6010i Maioqf 1953 L. s. MALOOF VISUAL ELECTRON FLOW INDICATOR 2 Sheets-Sheet 2 Filed Aug. 9', 1951 Ja an???" [earaJIMaZa 9 2m Patented Aug. 11, 1953 UNITED STATES PATENT OFFICE VISUAL ELECTRON FLOW INDICATOR Leon S. Maloof, Watertown, Mass., assignor to Lee Electronic Labs, Inc., Roxbury, Mass., a corporation of Massachusetts Application August 9, 1951, Serial No. 241,107

6 Claims. (01. 313108) As was described in my copending application Serial No. 211,904 filed February 20, 1951, with the increasing complexity of radar, electronics and communications equipment the problems of quick, efiicient service and maintenance become an important factor, and the need of some quick and infallible technique or device to facilitate the service and maintenance of all types of electronic equipment is vital. 1

In my above mentioned copending application one solution to such problems was to apply to a positively charged electrode of a vacuum tube, a spot of a suitable phosphor in a position in the path of the operational flow of electrons so that the spot glows as an indication of a normal electron current flow through the tube. This solution is not applicable to all types of vacuum tubes as the anode structure of some tubes encloses the cathode so that the portion of the anode in the path of the electron flow is not visible from without the tube. In other types of tubes the electron receiving portion of the anode structure is visible but positioned so near to the oathode that a phosphor applied thereto would be evaporated by the heat radiated. from the cathode.

It is accordingly the principal objects of this invention to overcome the above described limitations and provide means whereby it is possible visually to determine whether a vacuum tube is functioning properly while under normal operating conditions.

Other objects are to provide means for testing vacuum tubes which does not require the use of external equipment such as tube checkers, meters or oscilloscopes; which does not alter the electrical characteristics of the associated circuit of the tube being tested, which can be used in the circuits of existing apparatus without alteration, modification or additions thereto; which does not require that the tube being tested be removed from its socket or the associated equipment be shut down; which gives a continuous indication; which does not require any special skill or technique to use; which may be readily incorporated in existing types of electron tubes; which does not increase the interelectrode capacities or alter the normal characteristics of the tube with which it is used; which is safe to use; which is economical to manufacture and which can be produced by mass production techniques.

The invention attains these objects in electron discharge apparatus having within a transparent envelope at least a cathode for emitting an electron flow and an anode with a wall portion facing the cathode, this wall portion having a window in the path of the electron flow, by providing such apparatus with screen means emitting light under electron bombardment and with screen support means on the anode closely adjacent to the window and having a surface which is inclined to the plane of the window wall portion, the screen means being applied to the support means which is disposed to receive electron fiow passing through the window.

In another aspect, devices according to the invention comprise a screen supporting surface which has essentially the same area as the window, preserving the electrically eifective anode area regardless of anode modification by the Window.

In a preferred embodiment, the screen support means consists essentially of the cut-out window portion of the anode wall which portion protrudes louver-shaped outwardly from the window and carries the screen means on its inner surface, whereas, in another embodiment, the screen support means comprises a flange sur rounding at least part of the window and the screen means is applied to the inside of this flange.

These and other objects and aspects will be apparent from the following description of several specific embodiments of the invention referring to drawings wherein:

Fig. 1 is an isometric view with portions broken away of one embodiment of the invention;

Figs. 2, 3, 4 and 5 show alternate types of anode structures for the embodiment shown in Fig. 1;

Figs. 6 and '7 show alternate types of insulating spacers for the embodiment shown in Fig. 1;

Fig. 8 is an elevation view with portions broken away of a second embodiment;

Fig. 9 is a section on line 9-9 of Fig. 8;

Fig. 10 is an elevation view with portions broken away of a third embodiment; and

Fig. 11 is a section on line ll-ll of Fig. 10.

,The electron discharge device shown in Fig. 1 is generally similar to the double triode vacuum tube having the commercial designation 12AU7 having an envelope 12 of a transparent material such as glass. Located within the envelope l2 are two spacers l4 and I6 of mica or other insulating material which act as supports for two essentially identical sets or groups of electrodes which are entirely independent of one another with the exception of common heater connections so, that only one set will be described, it

3 being understood that the other set is similar in construction.

Each set of electrodes consists of a cathode k having an emitting surface for example of any of the alkaline earth oxides, well known to those skilled in the art, which copiously emits electrons when .raised to a high temperature by means of a heater (not shown) located within the cathode is. The ends of the cathode is are supported by the spacers I4 and i6 respectively: Electrical connections between-q'thec athode {c -its heater and associated external circuits (not shown) are made through pinscli which pass through seals 2c in the well known'manner.

Positioned on either side of the cathode k is a mounting support 22 for the;.oQntr, l1-eleetrpde, grid structure g. Outside of the grid structure g is arranged an anode structure a which'is generally box-like in shape so that electrons flow from the surface of the cathode it through the grid structure to the. inner surface. of; the anode structure wwhen the-tube: electrodes are connected: by means of the pinsm w'ith suitably. designed circuits such as arewelhknowrr in the 'art.

Located in the outer side-of the anode structure a is a window w, which in the case of -the embodiment shown-in Fig-1 is form-ed by punching or otherwise bending-a tab outwardly to form alouver 2-4; The inner surface s of-the louver 24 has applied thereto aspot of a suitablephosphor such as Willim-ite "on-othenmaterial which will glow. orfluoresceu'nder the influence of the electrons fromthe -cathode 70' which escape throughthe window: w;

- A1thoughinmanyapplications it is preferable to have the phosphored surface s of the louver 2d;- -1acingupwardly so:that= it can be observed from the-top of: the-tubewhenthe tube is enclosed withina shield: orthe-view blocked by adjacent circuit:components,v it will be understood that" the-:louven can be arranged to be viewed througlrthe-side wall ofthetube envelope ifthe configuration of the-associated equipment makes -such -an arrangement more desirable. Whomthe -louver -25-isarranged as is shown in Fig. 1, it is necessary that the spacer 14- either be made-of olear mica orthatopenings-such as the recesses; zeta provided-so that thedl-uorescence can be observed; Alternativelythe openings can be in the form=of-rectangularapertures 26st such as are shown-in Fig fi orcircular apertures -1 25b such as are shown in Fig. I '7;

'In Fig. 2-is:sho-wn-an anode structure aifor uSeinthe -tube-shown in=Fig. 1-, wherein the window wi is either circular or oval in shape having adjacent the -bottom port-ion thereof an internal flanges! whereupon is applied the phosphor material. I In the anQdestruetureaZ- (Fig: 3) the window m2 is a circularopening -upon the-bottcm of whoseside wall s2; whichis formed' by thethickness of the anode structuremateriaL is applied-the phosphonmaterial.

In Fig. 4 the" anode structure at is provided with arectangularopening which'is-glazed'with a sheet isot transparentmaterial; sucnas clear 1 ica, heldinplace bymeansof two tabs- 36: The phcsphor mater-ial is applied to the inner surface 83 on the miearsheet 'ril where the electrons will impinge thereupon and the glow- "therefrom can be seen through the-sheet; Alternatively-a circular window w ll such as shown in the anode structure-o l Fi'g;5)-,- can be-covered-by a flne mesl'r screenew Wih-ich-isspot weldedto the outer surfacei ofsltheeanode; structure.-

Phosphormaterial is applied to the screen wires as at $4.

The scope of this invention is not limited to tubes having a box like anode structure such as that shown in Fig. 1, but includes tubes having a cylindrical anode structure 415 such as the type 6BA6 tube shown in Figs. 8 and 9; or a plate type anode structure at such as the type 6AG5 shown in Figs;; lo and l1=. Although louyentype of windows w similar to those shown in 'Fig 1 are incorporated in the anode structures in the tubes shown in Figs. 8 and 10 respectively, it is to be understood; that windows similar to those illustrated in Figs. 2 through 5 or their equivalent may be; substituted therefor.

As-thepresence of the phosphor spots s has been found'in no way to efiect the performance .oncharaeteristiosvqf the tube, it can be used as a replacement for its conventional prototype without any change in the associate circuit. When the tube is operating normally the phosphorv spots. so fluoresce brilliantly enougheso that they can be seen ata. distance of several. feet in illumination of. ordinaryv intensity. so that by observing that the fluorescence is. of normal brilliancy a technician can Visually determine without: the. need: of. any test instrument. or tube checker that the following conditionsprevail:

(12) The emission of the cathodeislsufficient.

(2) The power supply. impressing voltage upon the: anodev is operating satisfactory.

(3) The tube is conducting i.- ethe presence of. plate current.

(4:) Present and relativestrength of modulatedinput carriersignals.

It is thus. possible. inapparatus such as computers where large numbers. of similar tubes are used, quickly torfind faulty tubes by observa tion. of. therelative. brilliancy. of the respective phosphor spots in adjacent tubesthusgreatly reducing the time. required to :isolate the tube. or circuit whereinthefault is located; The possibility of visual checking the-tubes also reduces the chance of-obtainingincorrect results due to an undetectedfailure ofsome portion of the computer and thus permits the elimination of expensive and complicated auxiliary checking circuits, thereby minimizing thecost-of construction.

Tubes incorporating/the above describedphosphor spotsalso haveapplication-inless complex circuits .such as in communication and radar equipment used by the armed forces, airlines and railroads, the. continuous functioning of which is. ail-ital: matten In suchequipment the technician can determine-by the reduction in the brilliancy' of the fluorescence of the phosphor spots the tubes in: which the emission is reduced without removing the tubes from- -t-he ir sockets thusreducingthe maintenancfi time required for routine checks-and eliminating to a great extent the necessity -for periodic replacements of all tubes.

Although I- have foundthat for general; appli oations the brilliant green fluorescence of Wiilignite the, mostsatisfactory color for h u s ot r. osph r a m diff rent fluorescing colors can be used to-advantage. For example by the use of. different phosphors upon therespectiveanodes 11-,zit is possibleto determine when: the tube: is used. in a flip-.flopf circuit which half of the tube is conducting. 1t; ;is:a ..So possi to s diffierentr phosphors linituhes. of thee-same. or: other types ;..:wh-ich are used-for edifi ferentzpurposesmaking it possible, for: example, for a technician to determine visually the tubes in the high, intermediate and audio frequency stages or having special functions.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall within the scope of the appended claims.

I claim:

1. A device for indicating the presence of electron fiow in electron discharge apparatus having within a transparent envelope at least a cathode for emitting an electron flow and an anode with a wall portion facing said cathode, said wall portion havin a Window in the path of said electron fiow, and screen means emitting light under electron bombardment, said device comprising screen support means on said anode closely adjacent to said window and having a surface which is inclined to the plane of said wall portion, said screen means being applied to said surface, which surface is disposed to receive electron flow passing through said window.

2. Device according to claim 1 wherein said surface of the supporting means has essentially the same area as the window, preserving the electrically effective anode area regardless of anode modification by the window.

3. Device according to claim 1 wherein said screen means substantially covers the entire area of said surface of said screen support means.

4. Device according to claim 1, wherein said screen support means consists essentially of the cut-out window portion of the anode wall which portion protrudes louver-shaped outwardly from the window and carries said screen means on its inner surface.

5. Device accordin to claim 1, wherein said screen support means comprises a flange surrounding at least part of said window and said 6 screen means is applied to the inside of the flange.

6. A device for indicating the presence of electron fiow in electron discharge apparatus having within a transparent envelope at least a cathode for emitting an electron flow and an anode with a wall portion facing said cathode, said wall portion having a window in the path of said electron flow, and screen means emitting light under electron bombardment, said device comprising a rectangular tab portion cut from said wall portion and bent outwardly from the wall portion, the area from which said tab is cut constitutin said window, which tab carries said screen means on the surface which is disposed to receive electron flow passing through said Window.

LEON S. MALOOF.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,994,726 Orth Mar. 19, 1935 1,994,733 Thompson Mar. 19, 1935 2,304,186 Litton Dec. 8, 1942 2,564,737 Szegho Aug. 21, 1951 2,565,533 Szegho et a1. Aug. 28, 1951 2,594,025 Jacobi et al Apr. 22, 1952 2,594,026 Jacobi et a1. Apr. 22, 1952 OTHER REFERENCES Kompfner, The Travelling-Wave Tube as Amplifier at Microwaves, Proceedings of the Institute of Radio Engineers, vol, 35, No. 2, February 1947, pages 124-127.

Varian et al., A High Frequency Oscillator and Amplifier, Journal of Applied Physics, vol. 10, No. 5, May 1939, pages 321-327, 

